Projection systems may be used to display still or video images. Some screens used in projection systems may receive a control signal as part of the process of displaying an image. Although one way to transmit such a control signal to a screen is via wireless (e.g., radio frequency) transmission, such transmission can create security issues. Specifically, the control signal can be intercepted by unscrupulous persons. Moreover, such transmission may cause problems as between projection systems. In particular, adjacent projection systems may suffer from crosstalk that interferes with proper control of the respective screens of the systems.